1. Field of the Invention
The invention relates to a suction electrocoagulator apparatus having an anticlogging tip and a suction control, finger operated venting port located at least partially downstream of the proximal end of the conductive cannula.
2. Description of Related Art
The coagulation of bleeding blood vessels using electrically conductive suction tubes also referred to as cannulas is a technique widely used for over two decades. A combined electrocautery and suction tube instrument is employed in surgery wherever excessive blood must be removed from the bleeding site in order to facilitate hemostat of bleeding vessels using the electrocautery feature of the instrument.
Commercially available suction coagulators made expressly for electrocautery hemostat procedures typically have the following common components:
(A) A hollow metallic tube having a suitable thickness of nonconducting electrical insulation on its exterior. The electrical insulation is absent from the last few millimeters on the tube's distal end in order to form an annular ring for electrocautery procedures. The sole purpose of the electrical insulation is to protect the patient and doctor from cautery burns that would result from contact with the outside of the metallic tube when it is energized.
(B) A non-metallic or electrically insulated handle. The handle includes a suction cavity or passageway running through its length that terminates in a suction fitting at one end for connection to a suction source. At its proximal end the handle is hermetically coupled to the hollow metallic tube so that the suction cavity of the handle communicates directly with the suction channel of the tube. The handle also may have a venting passageway that connects the main suction cavity with a vent hole on the handle's exterior. The surgeon uses finger pressure on the vent hole to control the amount of suction applied.
(C) A power cord, typically an insulated wire, is used to connect the suction coagulator to a high frequency current generator. The power cord enters the handle and is electrically connected to the proximal end of the metallic suction tube using various known connecting techniques.
The prior art electrocautery instrument described above works well when used for either suction or electrocautery. Unfortunately, two major problems arise when it is necessary to suction blood and cauterize at the same time in order to control excessive bleeding.
The first major problem arises because blood is electrically conductive. If blood reaches the surgeon's finger through the short venting passageway when the metal tube is energized, high voltage cauterizing current will pass through the blood in the passageway to the surgeon's finger. The rubber gloves typically used by the surgeon offer little protection from the high frequency, very high voltage energy and consequently a burn to the finger is likely to occur. For this reason, most manufacturers of electrocautery suction tubes caution surgeons not to use suction and cautery simultaneously.
Attempts have been made in the prior art to reduce the possibility of electrical shock. For example, U.S. Pat. No. 3,828,780 entitled COMBINED ELECTROCOAGULATOR-SUCTION INSTRUMENT issued on Aug. 13, 1974 to Charles F. Morrison, Jr., describes a suction coagulator using an exterior finger port and a passageway to the suction coagulator using an exterior finger port and a passageway to the suction cavity for controlling the suction applied to the tip of the instrument. According to the main teaching in that patent, the exterior vacuum control, finger vent hole is located upstream of the point where the venting air passageway communicates with the hollow interior cavity of the handle. The theory behind the structure described in U.S. Pat. No. 3,828,780 is that the location of the venting port with respect to the proximal end of the metallic tube and the venting air passageway prevents blood from reaching the surgeon's finger because in order to blood to reach the surgeon's finger, it must flow up the venting passageway in a direction opposite the direction of flow urged by suction. Unfortunately, independent experiments show that the theory works some of the time but a problem develops if the cannula suddenly clogs while the suction device is filled with blood and at the same time the surgeon's finger completely blocks the vent hole for maximum suction. Under such conditions, blood flow will stop and the suction vacuum will draw air out of the venting passageway causing it to fill with blood. It is apparent that the device described in U.S. Pat. No. 3,838,780 helps reduce burn hazards to surgeons but does not absolutely prevent its occurrence.
In order to demonstrate this problem in a clinical setting, a 75 pound pig was anesthetized and in incision was made to expose the viscera. Large blood vessels were located and severed to create pools of blood in the order of 2 cubic centimeters. The device described in U.S. Pat. No. 3,828,780 was used at maximum suction to suction the blood. After approximately a half cubic centimeter of blood had been drawn into the suction device, the tip of the cannula was pressed against the bleeding tissue which immediately clogged the tip. This process was repeated several times until the initial 2 cubic centimeters of blood was completely suctioned up. The procedure was repeated six times during the course of research and evidence of substantial amounts of blood in the venting passage was found after five of the six experiments. The same procedure was performed using the preferred embodiment of the present invention and there was no evidence of blood in the venting passageway after the experiments were completed.
The second major problem with regard to prior art devices such as described in U.S. Pat. No. 3,828,780 stems from the fact that a tube with an open distal end is not an efficient design for a suction device when used around tissue because the tip tends to clog easily. This occurs for several reasons. First, approximately 85% of the time conventional electrocautery devices are used to control bleeding from oozing beds such as those found after the removal of adenoids and tonsils. The suction tip of the device must be brought within several millimeters of the bleeding tissue to keep the field clear of blood in order to perform those procedures. As a result, tissue is constantly being drawn into the suction tip creating a clogging problem. That is one of the reasons for the use of a suction control finger operated vent hole such as described in U.S. Pat. No. 3,828,780. The surgeon uses the vent hole to stop suction in order to draw the suction tube away from tissue that is sucked into the suction end. This nuisance becomes magnified when the surgeon must touch tissue he is cauterizing while maintaining a field clear of blood using suction. The problem prompts many surgeons to use a Yankauer suction tube (typically metallic) alongside the cautery suction tube to guarantee suction capability during tonsillectomies. This is a dangerous practice because burns to the patient can occur if the cautery tip touches the metal Yankauer suction tube during activation. Second, during cautery procedures, tissue and coagulated blood tend to stick to the suction tip of the cannula causing it to eventually clog up. Numerous methods have been tried to prevent this, but none have been found adequate. The present invention according to its preferred embodiment provides secondary ports which when optimally located with respect to the primary port help to decrease clogging. This feature, in combination with an improved suction control, finger operated vent port arrangement helps to substantially reduce the possibility of electrical shock or burn to the surgeon.
U.S. Pat. Nos. 2,888,928; 3,595,234 and 3,610,242 were cited in the prosecution of U.S. Pat. No. 3,828,780 and are generally relevant to the state of the prior art.